Phase shift masks (“PSMs”) used in photolithography processes typically comprise a transparent (e.g., quartz) substrate having a phase shift pattern formed thereon, the phase shift pattern comprising, for example, a molybdenum silicon (MoSi) film formed on the substrate.
With ever decreasing features sizes and increasing costs of current and future photolithographic masks, the repair of masks becomes a substantial factor of the total mask production cost. One method of repairing PSMs involves the deposition of tetra-ethyl-ortho-silicate, (“TEOS”) on the area the be repairer and then reacting the TEOS to SiO2 using an electric beam (“e-beam”). Although such a repair is initially effective. TEOS is easily removed during wet cleaning of the PSM using a solution of sulphuric acid (H2SO4) and ammonia (H3), for example. As a result, such repairs are fairly temporary and must be made repeatedly over the life of the PSM.